使用MySQL用户定义变量在UPDATE语句上连接表名称

Question

我试图在UPDATE语句的表名上设置前缀。我必须在多个数据库上运行这个UPDATE语句几十次，每个数据库都有不同的表前缀。

下面的代码不起作用，但这是我想要完成的想法。

SET @prefix = 'prefix_'; 
SET @old = "old_value"; 
SET @new = "new_value"; 
UPDATE CONCAT(@prefix, 'table1') SET some_field = REPLACE(some_field, @old, @new); 
UPDATE CONCAT(@prefix, 'table2') SET some_field = REPLACE(some_field, @old, @new); 
UPDATE CONCAT(@prefix, 'table3') SET some_field = REPLACE(some_field, @old, @new); 

书面手动将...

UPDATE prefix_table1 SET some_field = REPLACE(some_field, 'old_value', 'new_value'); 
UPDATE prefix_table2 SET some_field = REPLACE(some_field, 'old_value', 'new_value'); 
UPDATE prefix_table3 SET some_field = REPLACE(some_field, 'old_value', 'new_value'); 

Answer 1

使用Dynamic SQL此，

SET @prefix = 'prefix_'; 
SET @old = "old_value"; 
SET @new = "new_value"; 

SET @sql1 = CONCAT('UPDATE ', @prefix, 'table1 SET some_field = REPLACE(some_field,?,?)'); 
SET @sql2 = CONCAT('UPDATE ', @prefix, 'table2 SET some_field = REPLACE(some_field,?,?)'); 
SET @sql3 = CONCAT('UPDATE ', @prefix, 'table3 SET some_field = REPLACE(some_field,?,?)'); 

PREPARE stmt1 FROM @sql1; 
PREPARE stmt2 FROM @sql2; 
PREPARE stmt3 FROM @sql3; 

EXECUTE stmt1 USING @old, @new; 
EXECUTE stmt2 USING @old, @new; 
EXECUTE stmt3 USING @old, @new; 

DEALLOCATE PREPARE stmt1; 
DEALLOCATE PREPARE stmt2; 
DEALLOCATE PREPARE stmt3; 

• Prepared Statements